Putting Databases on the Internet

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Putting Databases on the Internet

• Brenda LowndesComputing Services Department
• The University of Liverpool
• England

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Overview

• Why put databases on the Internet?
• How is data published to the Web?
• What software is available?

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Databases on the Internet

• Information in a database used to create Web
  pages
• Web browsers used to view or update a database

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Using database to create Web pages

• Company data is usually stored in a database.
• Data replicated in HTML pages results in
• Duplication of data and effort
• Inconsistencies in the data
• Difficulties in merging updates
• Web pages automatically updated when database
  updated

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Web browsers used to access data

• Familiar interface
• Data integrated with other information in
  companys web pages
• Platform and vendor independent front-end
• Client machine does not need database
  networking software
• Information can be made available to anyone on
  the Internet

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How is data accessed?

• HTML pages are generated from the database
• statically
• dynamically
• Java and JDBC
• run on the client
• run on the server

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Static pages

• Program runs offline to produce the HTML pages
• Pages copied into web server directories
• Can be automated and scheduled to run
• at specific times
• triggered by a database update

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When should you use static access?

• Non volatile data
• Fixed or small number of pages
• Predefined requests to the database

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Software for creating static pages

• Any program that can access the database and
  output HTML
• programming language and embedded SQL
• report writers
• database scripting language
• Database and Web development tools provide a
  Save as HTML option

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Dynamic Access

• HTML pages are generated from the database when
  the page is requested
• Data always up to date
• HTML forms can be used to define specific data
  that is to be retrieved
• Many different pages can be generated

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Creating pages dynamically

• Programs on the server access the database and
  output HTML
• Server extensions or filters embed data into
  HTML template files
• Server-side scripts access the database and
  output HTML

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Program on the server

• Print statements output the HTML page
• Usually run as a Common Gateway Interface (CGI)
  program

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CGI Program
Web Server
CGI
Web Server
HTML
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Client Server
Web Server
CGI
HTML
Client/server Access
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Running a Program
CGI
Web Server
Database Networking Software
HTML
Database Client
Database Networking Software
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Client Server
Web Server
CGI
Web Server
Database Networking Software
HTML
Database Networking Software
Database Server
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Client Server
Web Server
CGI
Web Server
ODBC Driver
HTML
Database Networking Software
Database Networking Software
Database Server
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Software for creating dynamic pages

• DBPerl
• Embedded SQL
• Database report writers
• Database scripting languages

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Template files

• Template specifies
• database location
• what data is required
• what HTML is output
• Template is processed by a
• Server extension or filter
• Server plug-in
• CGI script

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Templates
Web Server
HTML Template
Server Extension
Web Server
HTML
Database Networking Software
Database Server
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Advantages of using templates

• Pages easier to write than programs
• Requires only a knowledge of
• HTML
• how to specify an SQL query

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Software

• Software usually written for specific server
  extension
• Web development tools automate the process

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Internet Database Connector

• Extension to Microsoft Internet Information
  Server
• Uses two files
• .IDC file provides information about the database
  and the SQL queries used
• .HTX file provides the HTML template into which
  the data from the database is embedded

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Producing IDC files

• Microsofts database products have wizards to
  produce IDC/HTX files
• Microsofts Web development software
• Frontpage
• Visual Interdev
• Web development tools from other suppliers will
  also generate IDC/HTX files

25
Software for producing IDC files

• Save as IDC/HTX option in Microsoft Access
• Microsoft Frontpage
• Microsoft Visual Interdev
• Software from other software vendors

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Server-side scripts
Web Server
Active Page
Filter
Web Server
HTML
Client/Server
Database Server
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Active Server Pages

• Microsoft Internet Information Server 3.0
• Server-side execution environment
• Can access any ODBC database
• Output is HTML- suitable for any browser
• Maintain a connection to the database

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Stateless Connection

• The client requests the data
• The server connects to the database
• produces the HTML
• delivers the page to the client
• disconnects from the database

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Maintaining a Connection

• Servers maintain a session between subsequent
  requests from the client
• These servers can maintain a connection to the
  database
• Can define a record set and scroll through
  records
• Database connection can be closed by a request or
  timed out after a defined period of inactivity or
  when the server is shut down

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Client side Java and JDBC

• JDBC is a Java API for executing SQL statements
• JDBC statements in a Java applet are used to
  access virtually any relational database
• The Java applet is downloaded to the client
• The client establishes the connection with the
  database server

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Client side Java and JDBC
Web Server
Web Server
Java Applet
Java Applet
Java Applet
Database Server
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Server side Java and JDBC

• Java applet runs on the server
• JDBC driver on server maintains the connection
  with the database server

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Server side Java and JDBC
Web Server
Web Server
Java Applet
Java Applet
Java JDBC
Java Applet
Database Server
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What Tools are Available?

• List of software at
• http//www.liv.ac.uk/qq48/publications/html/dbweb
  .html